Matrix retainer



Dec. 29, 1959 Q R. B. THURMAN 2,918,724

MATRIX RETAINER Filed April 21, 1959 INVENTOR.

Arme/vm United States Patent O MATRIX RETAINER Robert B. Thurman, Sparta, Tenn.

Application April 21, 1959, Serial No. 807,931

4 Claims. (Cl. 3263) This invention relates to a dental instrument, and it more particularly relates to a matrix retainer.

It has long been the practice to use a matrix band during the process of filling teeth. The matrix, which is a thin band of sheet metal or the like, is placed around the tooth to be filled and across the cavity in the tooth so as to form a support or anvil against which the filling may press while it is being packed into the cavity.

One of the main difiiculties heretofore experienced with the aforesaid type of instrument has been to adequately prevent dislodgment of the matrix by the tongue, cheek or any other obstruction while it is in place. Another difiiculty has been the relative bulk of many prior type instruments and the lack of ease in handling them. Other prior instruments of this type have either been unduly complicated or so poorly constructed that they could not adequately perform their intended purposes with the desired amount of precision.

It is therefore one object of the present invention to overcome the above difliculties by providing a matrix retainer which does not tend to become loosened or dislodged when in the mouth.

Another object of the present invention is to provide a matrix retainer which is relatively simple in construction and easy to manipulate.

Other objects of the present invention are to provide an improved matrix retainer of the character described, that is easily and economically produced, which is sturdy in construction, and which is highly eflicient in operation.

With the above and related objects in view, this invention consists in the details of construction and combination of parts, as will be more fully understood from the following description, when read in conjunction with the accompanying drawing in which:

Figure 1 is a top plan view of a device embodying the present inveniton.

Fig. 2 is a side elevational view taken on line 22 of Fig. 1.

Fig. 3 is a plan view of a matrix utilized with the present invention.

Fig. 4 is a fragmentary view similar to Fig. 1, but showing the device in open position.

Referring in greater detail to the drawing wherein similar reference characters refer to similar parts, there is shown a matrix retainer, generally designated 10, which comprises a pair of oppositely curved spring-metal arms 12 having offset arcuate jaw portions 14. On each arcuate jaw portion 14 is pivotally connected a ratchet 16, the pivot being shown at 18. At the outer end of each ratchet 16 is provided a hook portion 20.

Extending inwardly from a position adjacent the intersection of each arm 12 with its offset portion 14 is an ear 22. Pivoted, as at 24, to each ear 22 is a link 26. These links 26 are pivoted to each other as well as to one end of a rod 28 by means of a pivot pin 30.

The opposite end of rod 28 is threaded, as at 32, and extends through an aperture in a bearing portion 34 at the intersection of the two arms 12. A nut 36 having a knurled knob portion 38 threadedly engages the rod 28 outwardly of the bearing portion 34.

In use, the hook portions 20 of ratchets 16 are adapted to selectively engage opposed corresponding slots 40 of a 2,918,724 Patented Dec. 29, 1959 matrix 42, the ratchets freely pivoting on their hinge pins 18 to permit such engagement. However, when the hooks 20 have been engaged in the appropriate slots 40, they are locked in position by means of collars 44, one such collar 44 being slidably positioned on each portion 14. The locking by collars 44 takes place by means of a frictional engagement around the inner end of the corresponding ratchet 16 (as shown in Fig. 1). To release the matrix 42, it is merely necessary to pull down the collars 44 to release the pivoted ratchets (as shown in Fig. 4).

With the matrix 42 in place and with the ratchets 16 locked in position by collars 44, the matrix 42 is bent into shape around the tooth by manipulating the knob 38 in one direction or the other to move the rod 28 in or out. When the rod 28 moves out, it spreads the links 26 to open the jaws of the instrument while, when the rod 28 moves in, it pulls in the links 26 to close the jaws and therefore to bend the matrix 42 into position around the tooth.

Although this invention has been described in considerable detail, such description is intended as being illustrative rather than limiting, since the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

l. A matrix retainer comprising a pair of bowed spring arms in opposed relation to each other and connected to each other at one end by means of an apertured bearing, an offset jaw portion at the free end of each arm, a ratchet pivoted intermediate its ends to each olfset jaw portion, a hook at one end of each ratchet, a collar slidable on each jaw portion and arranged to frictionally encompass the end of the corresponding ratchet which is opposite the end provided with the hook, and means to move the jaw portions toward and away from each other.

2. The matrix retainer of claim 1 wherein said means comprises a shaft axially movable through said apertured bearing, said shaft having linkage connecting it to each of said jaw portions, and means for retaining said shaft in axially adjusted positions.

3. The matrix retainer of claim 2 wherein said shaft is threaded at one end to receive a nut, said nut abutting against said apertured bearing and coacting with the threads on said shaft to form said means for retaining said shaft in axially adjusted positions.

4. In combination, a matrix and a matrix retainer, said retainer comprising a pair of oppositely bowed spring arms connected to each other at one end by means of a bearing member and provided at their opposite ends with arcuate jaws, a shaft extending through said bearing and having a pair of links at one end connecting it with said jaws, the opposite end of said shaft being threaded and engaged by an adjusting nut, said nut abutting said bearing, each of said jaws having a pivoted ratchet connected thereto, each ratchet having a matrix holding hook at one end and a tail portion at the other end, the pivot be ing intermediate said ends, a slidable collar on each jaw adapted to releasably engage the tail portion of the corresponding ratchet, and a matrix band having a plurality of slots at opposite ends engaged by said retainer by means of selective engagement of said hooks with respective slots in said matrix band.

References Cited in the file of this patent UNITED STATES PATENTS 424,790 Ivory Apr. 1, 1890 761,151 Cummings May 31, 1904 1,868,981 Ivory July 26, 1932 

